On the list of activities of a contact:
The oldest activity is on the top by default, it would be easier to have the latest at the top by default.
Rationale: you are more interested by what you've done with the contact lately than when you first met him/her.
NOTE: The default sort of "Status, Activity Date Ascending" makes sense for the Dashboard - which only shows Scheduled Activities. However, as noted above - sorting by Activity Date Descending is best for the Contact View >> Activity Tab.
We've changed the code so we can have different sorts depending on "context" of the activity listing.